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Abstract:

A 3D projection apparatus comprises a projector, and an angular array of
illumination optics coupled to an imager in the projector to create a
plurality of views for an 3D image. An array of projection optics is
coupled to the imager and a light source is coupled to the angular array
of projection optics.

Claims:

1. A 3D projection apparatus, comprising: a projector, which includes an
imager; and an angular array of illumination optics coupled to the imager
to create a plurality of views for an image.

2. The apparatus of claim 1, further comprising: an array of projection
optics coupled to the imager, wherein the angular array of illumination
optics is fixed spatially relative to the projector.

3. The apparatus of claim 1, further comprising: a light source coupled
to the angular array.

4. A holoform 3D projection display system, comprising: a plurality of
illuminators; an angular array of light guides coupled to the
illuminators; an imager coupled to the angular array of light guides, the
projector including an imager; and an array of projection lenses coupled
to the imager.

5. The display system of claim 4, wherein each of the illuminators
comprises: at least one of a light emitting diode.

6. The display system of claim 4, wherein each of the illuminators
comprises: at least one of a laser diode.

7. The display system of claim 4, further comprising: a mirror
arrangement coupled to the array of projection lenses to increase a field
of view.

8. A method to provide a 3D projection display, comprising: a projector
supplying light at a plurality of angles to an imager, to create an image
using an angular array of illumination optics; and directing the light by
the projector to an array of lenses.

9. The method of claim 8, further comprising: time multiplexing the
supplied light.

10. The method of claim 8, wherein the lenses have an arrangement
determined by the plurality of angles.

Description:

[0001] This application claims the benefit of U.S. Provisional Patent
Application No. 61/778,297 filed on Mar. 12, 2013; this application
claims the benefit of the provisional's filing date under 35 U.S.C.
§119(e), which provisional application is hereby incorporated herein
by reference in its entirety.

FIELD

[0002] Embodiments as described herein relate to three-dimensional ("3D")
display systems, and more particularly, to holoform 3D display systems.

BACKGROUND

[0003] Existing glasses-free flat panel 3D displays are based on
technologies developed in the early 1900s (e.g., lenticular lens and
parallax barrier). These displays have poor image quality and limited 3D
capabilities. The current glasses-free flat panel 3D displays present a
limited number different views (e.g., 5-9) of an image over a limited
horizontal field-of-view (e.g., 20 degrees). When viewed within the ideal
viewing range one sees two adjacent views simultaneously (one in each
eye) which creates the 3D effect. Outside of this field of view the sets
of views repeat (e.g., 1-2-3-4-5-1-2-3-4-5-1-2-3-4-5-1-2-3-4-5) which
causes an uncomfortable transition zone when users see view 1 with one
eye and view 5 with the other eye. This limited number of views prevents
users from getting a full 160-180 degree 3D view of a scene and the
transition zones and other visual artifacts (cross talk and moire) make
these displays unacceptable in most applications.

[0004] Generally, holography, and in particular electro-holography (moving
images) have the potential to present a true 3D image from a flat screen
display. Multiple user holographic displays do not exist today due to
high pixel count, high bandwidth and high compute power requirements.

[0005] Existing holoform rear and front projection displays use a static
holographic projection screen and a large number of individual projectors
to create a 3D viewing experience. This is achieved by creating a
hologram in only the horizontal direction while filling in the vertical
plane by diffusion similar in performance to a standard projection
screen. This one-dimensional hologram significantly reduces bandwidth
requirements and can be achieved with computer power available today.

[0006] Existing holoform systems most often use a large number of
individual projectors that make them large, noisy, power hungry and very
expensive. As a result, the existing holoform systems are not
commercially viable. Time multiplexing of a set of projectors in the
existing holoform system typically requires a motor-driven image scanning
system which results in additional artifacts (e.g., low luminance and
blur). These time multiplexed holoform systems require laser illumination
which introduces speckle in the image, and may provide safety concerns.
The image quality in the existing time multiplexed holoform systems is
low. Additionally, many exhibit reliability problems in addition to poor
image quality.

[0007] Holoform generally refers to a horizontal parallax only 3D
technology to direct different image information to each eye. In a
holoform 3D system, a special directional scattering screen is used to
limit where a viewer can see the appropriate image information. In a
holoform 3D system, the holographic screen is typically horizontally
segmented (vertically striped) with limited horizontal diffusion in each
segment and high diffusion in the vertical direction. Thus light passing
through each screen segment can be considered to pass unaffected along a
horizontal axis while it behaves as a normal projection screen in the
vertical direction. A projector illuminating this screen can effectively
be considered a point source that contains image information. If only one
projector were employed to illuminate such a screen any viewer would see
only a single vertical stripe of the projected image (which is
potentially different for each eye) where the vertical information (color
and intensity) of the image at that horizontal position on the screen can
be seen unaffected. A second projector will create a second stripe and
when a sufficient number of projectors are employed in a horizontal
arrangement a whole image will be seen over the entire screen that varies
in each eye as well as every different viewing position in front of the
screen. A small horizontal diffusion is added to each screen segment to
improve horizontal uniformity and limit the number of projectors required
to illuminate a full image on the entire screen.

[0008] Typically, when the image is different in each eye, 3D is
perceived. This image information can come from the same projector or a
different projector depending on the arrangement. Vertical stripes of
image information are presented by each imager to fill the light field,
for example, a viewing space. The field of view, for example, a
horizontal angular limit where an image is visible, is typically
controlled by the number of projectors, the magnification of each
projection lens, and in some cases, the angular distribution of the image
information. With a large angular distribution, image information can be
presented over nearly 180° field of view. Such a large field of
view will be required to work in any tiling application such as a video
wall application.

[0009] In an existing holoform system a reasonably large number of
independent projectors are typically used to illuminate the holoform
screen. The existing systems remain costly because of the relatively
large number of projectors that is required to illuminate a screen even
with only a limited field of view.

[0010] One way to reduce cost is to time multiplex a smaller number of
projectors to create the large number of images that would have been
created by the individual projection systems. Existing time multiplexed
holoform systems have moving optical elements, such as a scanning or
rotating mirror or prism which can deflect each image to a different
viewing zone. For these systems, a significant amount of time is required
to actually move the mirror and to stabilize the mirror before a new
image is projected onto it. This further limits the time light is
projected and therefore the brightness of the image. Rotating the mirror
or prism in a continuous fashion to eliminate the delay in projecting the
new image causes the image to move across the screen as it is projected.
This effectively blurs the image resulting in reduced contrast and
resolution, and creates substantial 3D crosstalk because at least a
portion of each image stripe crosses a stripe boundary as formed on the
screen.

SUMMARY

[0011] Embodiments of apparatuses and methods to provide a holoform 3D
projection display are described. In one embodiment, a 3D projection
apparatus comprises an image forming element, for example, a reflective
DLP micro-mirror device or liquid crystal on silicon (LCOS) imager,
coupled to an angular array of illumination optics to create a plurality
of views for an image. Furthermore, an array of projection optics is
coupled to each of the illumination optics array sources, where each of
the projection optics array elements is provided an image by the same
image forming element.

[0012] In one embodiment, a holoform 3D projection display system
comprises a plurality of illuminators and an angular array of light
guides coupled to the plurality of illuminators. An image forming device
is coupled to the angular array of light guides and an array of
projection lenses is coupled to the each of the illuminators. In one
embodiment, the plurality of illuminators comprises at least one of a
light emitting diode or a laser diode. In one embodiment, a mirror
arrangement is coupled to the array of projection lenses to increase a
field of view of the image.

[0013] In one embodiment, light is supplied at a plurality of angles to
the image forming device to create an image using an angular array of
illumination optics. The supplied light is time multiplexed. The light is
directed by the image forming element to an array of lenses. In one
embodiment, the lenses have an arrangement determined by the plurality of
angles which enables them to collect light from each individual set of
illumination optics.

[0014] In one embodiment, a transmissive image forming element is used to
form the image in each individual angular light path as provided by the
illuminator, light guide, and projection lens arranged in an array.

[0015] Other features and advantages of embodiments will be apparent from
the accompanying drawings and from the detailed description that follows
below.

BRIEF DESCRIPTION OF DRAWINGS

[0016] The present invention is illustrated by way of example and not
limitation in the figures of the accompanying drawings, in which like
references indicate similar elements, in which:

[0017] FIG. 1 shows a schematic representation of a top view of an
exemplary embodiment of a holoform light engine;

[0018] FIG. 2 shows a diagram of an exemplary embodiment of a system
comprising a holoform light engine and a mirror arrangement that
increases a field of view;

[0019] FIG. 3 shows a schematic representation of a side view of an
exemplary embodiment of a holoform light engine;

[0020] FIG. 4 is a view of a Table 1 showing DLP imagers for an exemplary
embodiment of a holoform light engine;

[0021] FIG. 5 shows a schematic representation of a top view of an
exemplary embodiment of a portion of a holoform light engine indicating a
separation distance for two adjacent horizontal subprojections; and

[0022] FIG. 6 shows a diagram illustrating an exemplary embodiment of an
illuminator used in a holoform light engine.

DETAILED DESCRIPTION

[0023] The embodiments will be described with references to numerous
details set forth below, and the accompanying drawings. The following
description and drawings are illustrative of the embodiments and are not
to be construed as limiting. Numerous specific details are described to
provide a thorough understanding of the embodiments as described herein.
However, in certain instances, well known or conventional details are not
described in order to not unnecessarily obscure the embodiments in
detail.

[0024] Reference throughout the specification to "at least some
embodiments", "another embodiment", or "an embodiment" means that a
particular feature, structure, or characteristic described in connection
with the embodiment is included in at least some embodiments as described
herein. Thus, the appearance of the phrases "in at least some
embodiments" or "in an embodiment" in various places throughout the
specification are not necessarily all referring to the same embodiment.
Furthermore, the particular features, structures, or characteristics may
be combined in any suitable manner in one or more embodiments.

[0025] Embodiments of apparatuses and methods to provide a holoform 3D
projection display are described. In one embodiment, a 3D projection
apparatus comprises an image forming element coupled to an angular array
of illumination optics to create a plurality of views for an image. An
array of projection optics is coupled to the image forming element. An
illuminator is coupled to the angular array of illumination optics.

[0026] In one embodiment, a fundamentally new type of time multiplexed
holoform 3D display comprises a single projector and an angular array of
illuminating light pipes to create a large number of views required. The
time multiplexed holoform 3D display as described herein has no moving
parts and as result has better performance and reliability. In one
embodiment, the time multiplexed holoform 3D display is designed to use a
light emitting diode ("LED") illumination to eliminate the speckle and
eye safety issues associated with lasers.

[0027] A light engine that is the core of the time multiplexed holoform 3D
display meets or exceeds image quality objectives. In one embodiment, the
light engine includes a digital light projection ("DLP")-based imager
with electronics and software, an LED illuminator, a multiple light pipe
assembly with a corresponding field lens array, and holoform projection
screen.

Advantage of Angular Distribution

[0028] A holoform 3D system as described herein has an advantage of no
moving parts and therefore no associated delays or resolution loss (e.g.,
blurring) which can come from scanning images over a surface. Each light
engine is capable of creating multiple full color images directed at
different angles onto a holoform screen such that a high resolution 3D
image can be perceived by multiple viewers in different viewing positions
over a wide angle of view. For higher resolutions at least two of these
light engines can be combined to double the number of imaging systems
with a substantially lower cost to a large image field of view.

[0029] FIG. 1 shows a schematic representation of a top view 100 of an
exemplary embodiment of a holoform light engine 110. The engine 110
includes at least one light source. In one embodiment, the light source
includes illuminators such as a illuminator 101 ("Illuminator 1") and an
illuminator 102 ("Illuminator 17") that include at least one light
source. An angular array of light guides including e.g., a light guide
103 ("Lightpipe 1") and a light guide 104 ("Lightpipe 17") coupled to the
corresponding light source. An image forming element 109 is coupled to
the angular array of light guides. An array of projection lenses
including e.g., lens 105 ("Lens 1") and lens 106 ("Lens 17") is coupled
to the projector 109. In one embodiment, projector 109 represents a DLP
imager. In one embodiment, the guides, such as guide 103 and 104
represent optical fibers. In one embodiment, the image forming element is
one of the DLP imagers produced by Texas Instruments Inc., ("TI")
headquartered at Dallas, Tex., United States.

[0030] Typically, in DLP projectors, an image is created by
microscopically small microelectromechanical ("MEMS") mirrors (e.g., laid
out in a matrix on a semiconductor chip, known as a Digital Micromirror
Device (DMD). Each mirror represents one or more pixels in the projected
image. These mirrors can be repositioned rapidly to reflect light
supplied by an illuminating source to create a gray scale with each
sequential Red/Green/Blue illumination as known to one of ordinary skill
in the art of DLP light projectors.

[0031] In one embodiment, a key to the 3D holoform system disclosed herein
is an illumination system. Instead of using scanning optics to direct
each view to the proper projection angle an array of illuminating light
guides are used to define each view. A single DLP imager 109 is
sequentially illuminated by each fiber as shown in FIG. 1. The mirrors of
the DLP direct the light from those pixels necessary for the image to the
appropriate projection lens, such as lens 105 and 106, arrayed
horizontally and defined by the illumination fiber angle. The mirrors of
the DLP direct the light from dark pixels away from this array of lenses.
As shown in FIG. 1, the alignment of the lens and appropriate
illuminating fiber also creates the angle which directs illumination into
a specific set of viewing zones from each lens.

[0032] A clear advantage of the system described herein is that no moving
optics are employed and therefore the delays associated with them are
omitted. Light can be generated in any illuminator nearly instantaneously
for rendering into any of the views. In one embodiment, each illuminator
includes at least one light emitting diode directing illumination into
each view and optics for focusing this light into each light pipe. These
optics also directs this illumination into the light guide (e.g., optical
fiber) with appropriate angular extent (numerical aperture). The fiber
effectively conserves the angular extent of the light from the
illuminator to the point of emission where this light illuminates the
imager. The light is directed by the imager into the appropriate
projection lens with the appropriate image information. In one
embodiment, the light can be directed into the light pipe to allow
expansion onto the imager or remain effectively collimated. This can be
controlled by at least one of the illumination source, optics, and shape
of the light pipe.

[0033] The geometry of the system facilitates its operation. As shown in
FIG. 1, a radius of illumination ri and a radius of an angular lens
arrangement rL are defined by the angular extent of the illumination
and angular space occupied by each view, as well as the imager, lens, and
illumination fiber dimensions. As with most holoform systems, the best
functionality comes with the largest number of views using the smallest
possible angular resolution. These parameters further affect the
brightness and system complexity. In a manufacturable system a rigid
skeleton would be designed to hold all components in their appropriate
positions. The components could be interchangeable for various systems as
defined by their intended use.

[0034] In an embodiment where more angular resolution is desired, two
systems are combined, one inverted above the other, and offset by half
the angular view space of each lens. In such a case one illuminator is
used to illuminate 2 fibers, one in each system because two separate
imagers direct appropriate information to the same screen. In an
embodiment, where information between views is not substantially
different, a single illuminator illuminates multiple views in the same
system. This may not be desirable in a fully functional system where any
information may be desired for display at any time, but may be applicable
to some applications such as video walls where fixed, or busy patterns
are desired.

[0035] In an embodiment, the illuminator contains at least one red, one
green, and one blue light source (e.g., LED, laser diode) for a full
color image. In an embodiment, both color and gray scale are controlled
by time multiplexing of the illumination and power applied to the light
source. Theoretically the current used to drive a LED or laser diode in
each illuminator is the continuous power specified by the manufacturer
multiplied by the fraction of the frame in which it is used. If each
system employs a reasonably large number of views the instantaneous power
can be made very high in order to conserve brightness. In practice this
may not be as large as the theoretical limit.

[0036] The use of LEDs can reduce cost and eliminate the speckle at a cost
in a system complexity and image intensity as each subprojector should be
designed with a "large" angular field of view. The laser diode can reduce
system design limitations because the numerical aperture of the
illumination is near zero. Given the tradeoff between these two types of
illumination some compromise can be found where speckle is significantly
reduced by reducing the numerical aperture of the LED without
substantially limiting the image intensity.

[0037] FIG. 1 shows a system defining 17 subprojectors. This is not a
limitation of the system. More subprojectors can be added, or fewer used,
depending on the fundamental optical parameters of the system. To this
point, the output of each of these subprojectors, such as output 111 has
been loosely referred to as a view. A "view" is actually a 2D image of
anything taken at a specific angle and orientation.

[0038] In a holoform system the images projected by each of the
subprojectors are vertical segments of the views assembled together such
that an image is perceived over the entire screen at any eye location in
the viewing space. These vertical segments are defined by the screen, the
field of view and magnification of each projection lens, the resolution
of the imager, as well as the orientation of the projection lens. It is
possible that the 17 projector subsystems actually project segments of
far more than 17 views. Thus the resolution of the system is not actually
limited by the number of subprojectors assembled into the holoform light
engine. There is still a benefit to keep the horizontal angular space
parameter 112 (Φs) as small as possible but it is not directly a
limitation of the system. Failure mechanisms can include gaps in the
image or loss of 3D perception in specific viewing positions. These
failure mechanisms can also be compensated by increasing the imager
resolution or reducing the projection lens field of view.

[0039] FIG. 2 shows a diagram 200 of an exemplary embodiment of a system
comprising a holoform light engine and a mirror arrangement that
increases a field of view of the projected 3D image. A system 200
comprises a holoform light engine 110, a mirror arrangement including a
mirror 203 and a mirror 204. In an embodiment, an angular distribution of
projected images on a holoform screen is insufficient for a holoform
projection system. The projectors themselves need to project on the
screen from a wide range on angles and positions for a large field of
view. Given an angular distribution this is best accomplished by using
mirrors, such as mirrors 203 and 204. The reflection from the mirrors
increases the field of view by effectively adding more views, such as a
view 206 to existing views, such as view 202 and a view 202 from
positions outside of the enclosure, as shown in FIG. 2. In one
embodiment, mirrors 203 and 204 are substantially parallel mirrors. In
one embodiment, mirrors 203 and 204 are curved. In one embodiment,
mirrors 203 and 204 are part of a cylinder mirror.

[0040] FIG. 3 shows a schematic representation of a side view 300 of an
exemplary embodiment of a holoform light engine. The engine includes an
illumination fiber array 301, an imager 302, a beam dump 303, and a lens
array 304. In one embodiment, the engine represents a portion of the
holoform light engine 110 depicted in FIG. 1. In one embodiment, the
imager 302 is a DLP imager. In another embodiment, the imager of the
holoform light engine is a liquid crystal on silicon (LCOS) imager (not
shown). In the system using a LCOS imager technology there is no dump
beam to be accommodated but the fundamental speeds of LCOS devices are
presently too slow to generate multiple images into many subprojectors.
The DLP imager has sufficient speed, but the dump beam (reflection from
dark pixels or the negative image) cannot be accommodated in the
horizontal plane as it is fully occupied by optics necessary to generate
the many views needed to be directed at the holoform screen. Thus the DLP
imager 302 needs to dump the negative image information into the vertical
plane into a beam dump 303, as shown in FIG. 3.

[0041] In an embodiment, the parameter Φv is a full tilt of the
DLP pixel mirror. This effectively guarantees that the vertical image has
been fully separated before the adjacent horizontal images regardless of
a horizontal angular space Φs. In the interest of keeping
Φs as small as possible this becomes less important and it is
found that the existing DLP imagers can be accommodated except those that
dump the negative image in the horizontal plane.

[0042] FIG. 4 is a view 400 of a Table 1 showing the DLP imagers that are
commercially available today for an exemplary embodiment of a holoform
light engine. In an embodiment, not all commercially available DLP
imagers have sufficient speed to support 20+ sub-projectors on a single
device. Further limitations may include the mirror tilt direction. Mirror
hinges are typically connected to the pixel corners and therefore the new
diamond device, DLP3000, may be a good choice. This device is not
acceptable for this application because the pixel mirrors tilt
horizontally. In all other devices the mirrors tilt at a 45 degree angle
to the horizontal and vertical. While this is not ideal it can work for
all subprojector designs which occupy a horizontal angular space
(Φs) of 6 degrees or less, as long as the vertical size of the
imager is smaller than the horizontal dimension. If a smaller angular
space is chosen one needs to be careful to ensure that the negative and
positive image will separate in, at least, the same distance that the
horizontal beams of adjacent views will separate.

[0043] Table 1 also shows the number of frames which can be addressed on
each imager as a function of time. The DLP7000 is capable of 32,000 frame
updates each second. Such a device could support 22 full color (24 bit)
views on a single imager. The most common chroma subsampling, widely used
by many high end digital video formats, (4:2:2) reduces both red and blue
images to 4 bits each as it uses the same color for two adjacent pixels
at different brightness. This results in the possibility of addressing as
many as 33 horizontal subprojectors with one imager.

[0044] While the DLP7000 imager has a sufficient speed for the system,
there may be a problem with the dimensions of this imager. This imager
has a horizontal dimension of about 14.2 mm which results in significant
restrictions of a horizontal view space and illumination angular extent.
In the exemplary 17 subprojector system depicted in FIG. 1 where each
view occupies an angular space of 6 degrees, using an illumination
angular extent of only 2 degrees requires a distance of about 40 cm to
separate adjacent views. This can result in low magnifications and
therefore limited field of view in the 3D image space.

[0045] FIG. 5 shows a schematic representation of a top view 500 of an
exemplary embodiment of a portion of a holoform light engine indicating a
separation distance for two adjacent horizontal subprojections. The
engine includes light guide fibers, such as light guide fibers 501 and
502 that direct illuminating light to an imager 503 having an imager
normal axis 507. Imager 506 has a dimension Xj 506. Imager 503
directs light from the light guide fibers 501 and 502 to form an image A
508 and an image B 509. In one embodiment, the engine represents a
portion of the holoform light engine 110 depicted in FIG. 1. An image
separation distance parameter ds indicates the minimum spacing
required to separate the views to form images 508 and 509, and is also
the minimum back focal length required for each projection lens. In
reality this distance may need to be as much a twice this dimension due
to physical/mechanical constraints of the projection lenses themselves. A
lens of this design will require shifting significant cost to the lens
array to accommodate this very long back focal lengths.

[0046] Reducing the diagonal dimension (e.g., dimension 506) of the imager
to 0.3 inch can be a huge benefit to this system. For the same
illumination and view dimension the parameter ds now falls to 19 cm.
This is a far more manageable lens design. Further reduction of the
illumination angular extent from 2 to 1.5 degrees reduces ds to 13
cm (5 inches). This again is a much more appropriate design parameter for
projection lenses. In an embodiment, in a manufacturable holoform 3D
system the input lens array (the field lens element) can be designed as a
single freeform optic. This can significantly reduce the additional space
required between each view that would be necessary to accommodate round
lenses and the associated mechanics for positioning.

Further Optical Considerations of the Holoform Light Engine

[0047] The pertinent parameters are shown in the FIGS. 1-5. As described
herein, an important limitation is the separation of adjacent images from
each subprojector before reaching the projector lens array. This is
expressed in an equation as follows:

ds=xi/sin(Φs-2Θn)

where xi is a horizontal dimension of the imager and Θn
is an angular extent of the illumination. This is identical for vertical
image separation where the x imager dimension is replaced by the vertical
(y) dimension. Given that x is the larger dimension vertical image
separation can commonly occur in a shorter space. Note that ds
approaches infinity in the limit that Φs=2Θn. Thus
another limitation on Φs is as follows:

Φs>2Θn

[0048] This restriction effectively limits the illumination source to a
laser diode for small Θn. Both parameters further affect the
design of the projection lens, the dimensions of the light guide and
imager, as well as ri and rL. Furthermore, the angular space of
each subprojector (Φs) depends on the projection lens dimensions
and the optical speed of the lens (magnification/throw) as well as the
back focal length. A long back focal length will allow more lenses to be
fit in the plane of the lens array, and therefore more subprojection
systems which can provide more views, but it can also adversely affect
lens dimensions and lens optical speed.

The Illuminator

[0049] FIG. 6 shows a diagram illustrating an exemplary embodiment of an
illuminator 600 used in a holoform light engine. The illuminator 600 can
represent one of the illuminators depicted in FIG. 1. The illuminator 600
comprises an X-cube 601 and light sources 602, 603, and 604 that supply
light through corresponding lenses, such as aspherical lenses 605, 606,
and 607 and through X-cube 601 to a fiber light guide 608.

[0050] As described herein, the restriction of the illumination angular
extent may require the use laser diodes for illumination. The reduced
wavelength dispersion of these devices allows for better beam shaping to
more efficiently illuminate the fiber (light pipe) at the appropriate
angular extent. The use of the diode laser (LD) has no additional
constraints over the use of any LED. The efficiency, switching speed, and
overdrive capacity are excellent and have all the same physical
constraints as standard semiconductor LEDs. An effective and simple
design for the illuminator is shown in FIG. 4. A simple aspherical lens
at the output of each laser source (e.g., LED, or laser diode) can
effectively collimate the beam and an x-cube can combine the illumination
of each LD to illuminate the fiber light pipe. The x-cube is used for
illumination purposes and therefore need not be of the same specification
as those used to combine images in many 3 panel projection systems.

[0051] In an embodiment, a light guide fiber can be used to improve
collection and shape the illumination. With a small angular extent of the
illumination the output face of the fiber can be only slightly smaller
than the imager itself, thus improving light collection. The fiber can
also be tapered to better shape the output. A small increase in dimension
results in better collimation. Furthermore, the fiber can act as an
integrator resulting in a very uniform illumination. This illumination
light pipe fiber can also be used to accommodate different imager aspect
ratios and dimensions. A round input can be used with a rectangular
output with the same aspect ratio as the imager. While this changes the
angular extent of the illumination it can further improve the
illumination uniformity and illumination area resulting in an additional
gain for the illumination lost to the angular extent constraint.

Image Distortion

[0052] The images produced by the subprojectors at the relatively oblique
angles may result in distortion. These images may be wider than those
projected at an angle relatively normal to the imager. This will not be a
problem based on the fact that the projected information is not actually
an image but an assembly of stripes (image segments) that make up
multiple views. Adjusting any distortion in each segment will actually be
simpler than adjusting a full image distorted by oblique reflection.
Regardless, this can be most easily managed at the imager and only
requires that the width of each segment being imaged is not equal to one
pixel.

[0053] In another embodiment, an adjustment in the manufacturing of the
screen is made. Because holoform screens are produced as regular
holograms, there is no requirement that the horizontal diffusion remain
uniform for all illumination angles. A larger diffusion of oblique angle
rays can he made equal to the size correction for the segment resulting
in a more uniform image over the surface. This can also be used to an
advantage of the system. There can be many advantages to such a design.
For example, this can be used to further increase the field of view or
even "fill" large angular extents with what amounts to 2D images. This is
a significant advantage for applications like video walls where limited
field of view will result as blank portions of the screens that are not
designed to project into those angles.

Holoform Brightness Gain

[0054] A limitation of this design may be illuminating a small angular
extent while delivering sufficient brightness to the image, especially in
a video wall application. This limitation, in conjunction with the
extensive time multiplexing required by the holoform system may result in
such significant loss of light that it cannot be compensated by larger,
more powerful, illuminators.

[0055] An advantage to brightness in the holoform system is the screen
gain due to limited horizontal diffusion. A typical 2D screen projects
most of its light (50%) into a horizontal angle of 54 degrees. This still
results in limited brightness at larger angles. Still each projector used
in a holoform system described herein may appear as much as 20 times
brighter than the same projector used in a 2D application.

[0056] Another advantage is that multiple subprojectors are required to
build up each view. In the example above 2×17 projectors are used
to project into the same angular extent. This results in an additional
gain of 34× if all projectors are assumed to have the same 2D
brightness. These gains may be sufficient to offset the losses due to
small angular extent directed to each illumination fiber and extensive
time multiplexing.

[0057] Thus, with proper design a high resolution, reduced cost, 3D image
can be produced using the embodiments of the light engine having a very
large field of view as described herein. Proper management of the optical
design tradeoffs is used to realize any specific application, e.g., a 3D
digital signage video wall. The angular distribution design as described
herein is a key to realizing the large field of view. Furthermore, the
problem of image blurring due to moving optics is eliminated.

[0058] In the foregoing specification, the invention has been described
with reference to specific exemplary embodiments thereof. It will,
however, be evident that various modifications and changes may be made
thereto without departing from the broader spirit and scope of the
invention. The specification and drawings are, accordingly, to be
regarded in an illustrative rather than a restrictive sense.